The UN Security Council has plenty of reasons to respond forcefully to North Korea for its sinking of a South Korean naval ship. But one reason stands out: The South Koreans themselves need to know where the world stands on North Korea’s rising belligerency.

For a people who are on the front lines of a still-hot remnant of the cold war, South Koreans have become too complacent in recent years about the North Korean threat, especially its apparent possession of atomic weapons. Violent provocations, such as the March 26 torpedoing of the Cheonan that left 46 sailors dead, can be quickly forgotten in a country that’s mainly focused on remaining an export giant.

The old desire of South Koreans to reunite the two halves of the peninsula began to melt away in the 1990s after they saw the high cost that former West Germany paid to absorb the former East Germany. Also adding to their nonchalance has been the so-called “sunshine” diplomacy” of previous presidents, and the cozying up to North Korea with trade, aid, and tourism in hopes of stabilizing its economy and preventing it from a collapse.

This rising indifference in the South is just the trend that North Korean leader Kim Jong-il has long sought. He hopes to weaken the South’s resolve as one way to eventually break its military alliance with the United States.